Cervical carcinoma and several other human papillomavirus (HPV)-induced malignancies are a global public health problem, thus novel treatment modalities are urgently needed. Immunotherapy is an attractive option for treatment of infection and (pre)malignant lesions. However, previous approaches—focusing on the induction of cytotoxic CD8+ T cells—have as yet not yielded substantial clinical successes. Since CD4+ T cells have been shown to be crucial for the induction and maintenance of cytotoxic CD8+ T cell responses, and more recently to be also important for direct anti-tumor immunity, HLA class II-restricted epitopes are intensively investigated to improve the efficacy of peptide-based HPV immunotherapy.
High-risk types of human papillomavirus (HPV) are associated with several malignant diseases, including cervical carcinoma, other anogenital tumors, and oropharyngeal carcinomas (zur Hausen H. 1987. Papillomaviruses in human cancer. Appl Pathol 5: 19-24; Bosch F X, et al. The causal relation between human papillomavirus and cervical cancer. J Clin Pathol 55: 244-65; Gillison M L, et al. 2012. Human papillomavirus and diseases of the upper airway: head and neck cancer and respiratory papillomatosis. Vaccine 30 Suppl 5: F34-541-3). Natural history studies indicate that nearly every sexually active individual will acquire at least one high-risk HPV infection during their lifetime (Baseman J G, Koutsky L A. 2005. The epidemiology of human papillomavirus infections. J Clin Virol 32 Suppl 1: S16-24, Schiffman M, Castle P E, Jeronimo J, Rodriguez A C). Fortunately, the majority of HPV infections are eradicated by the host immune system within 1-2 years of acquisition (Woodman C B, Collins S I, Young L S. 2007. The natural history of cervical HPV infection: unresolved issues. Nat Rev Cancer 7: 11-22, Rodriguez A C, et al. 2010. Longitudinal study of human papillomavirus persistence and cervical intraepithelial neoplasia grade 2/3: critical role of duration of infection. J Natl Cancer Inst 102: 315-24), and only <1% of infected people develop HPV-mediated cancers (Evander M, et al. 1995. Human papillomavirus infection is transient in young women: a population-based cohort study. J Infect Dis 171: 1026-30, Koutsky L. 1997. Epidemiology of genital human papillomavirus infection. Am J Med 102: 3-8). Why some individuals clear the viral infection, while others do not, is still incompletely understood. Accumulating data suggest that both cytotoxic CD8+ T cell (CTL) and CD4+ T helper (Th) cell responses play a pivotal role in the control and clearance of HPV infection (Stanley M A. 2001. Immunobiology of papillomavirus infections. J Reprod Immunol 52: 45-59; Welters M J, et al. 2003. Frequent display of human papillomavirus type 16 E6-specific memory t-Helper cells in the healthy population as witness of previous viral encounter. Cancer Res 63: 636-41; Nakagawa M, et al. 2000. Persistence of human papillomavirus type 16 infection is associated with lack of cytotoxic T lymphocyte response to the E6 antigens. J Infect Dis 182: 595-8; van der Burg S H, et al. 2002. The status of HPV16-specific T-cell reactivity in health and disease as a guide to HPV vaccine development. Virus Res 89: 275-84). To date, however, the majority of therapeutic HPV vaccines have been designed to elicit tumor-specific CTL responses (Ressing M E, et al. 2000. Detection of T helper responses, but not of human papillomavirus-specific cytotoxic T lymphocyte responses, after peptide vaccination of patients with cervical carcinoma. J Immunother 23: 255-66; Kaufmann A M, et al. 2002. Safety and immunogenicity of TA-HPV, a recombinant vaccinia virus expressing modified human papillomavirus (HPV)-16 and HPV-18 E6 and E7 genes, in women with progressive cervical cancer. Clin Cancer Res 8: 3676-85; Garcia F, et al. 2004. ZYC101a for treatment of high-grade cervical intraepithelial neoplasia: a randomized controlled trial. Obstet Gynecol 103: 317-26). Unfortunately, only disappointing clinical outcomes have been observed, with the exception of one study with synthetic long peptides in vulvar intraepithelial neoplasia (Kenter G G, et al. 2009. Vaccination against HPV-16 oncoproteins for vulvar intraepithelial neoplasia. N Engl J Med 361: 1838-47). Exclusive targeting of HLA (human leukocyte antigen) class I-restricted CTL HPV epitopes, without involving specific T-cell help, can lead to suboptimal and short-lasting CD8+ T cell responses. The lessons learned from these clinical studies lead to a rethinking of therapeutic anti-HPV vaccine design.
Among the eight HPV proteins, E2, E5, E6, and E7 are regarded as being crucial for HPV immune escape and malignant progression. E2 and E5 are expressed soon after infection, prompting HPV immune escape mechanisms and initiating carcinogenic progression (Bellanger S, et al. 2011. Tumor suppressor or oncogene? A critical role of the human papilloma-virus (HPV) E2 protein in cervical cancer progression. Am J Cancer Res 1: 373-89; Xue Y, et al. 2012. Loss of HPV16 E2 Protein Expression Without Disruption of the E2 ORF Correlates with Carcinogenic Progression. Open Virol J 6: 163-72; Maufort J P, et al. A role for HPV16 E5 in cervical carcinogenesis. Cancer Res 70: 2924-31; Ganguly N. 2012. Human papilloma-virus-16 E5 protein: oncogenic role and therapeutic value. Cell Oncol (Dordr) 35: 67-76). E6 and E7 as major transforming proteins are constitutively expressed in both premalignant and advanced lesions, making them ideal targets for immunotherapeutic approaches for HPV-induced malignancies (zur Hausen H. 2000. Papillomaviruses causing cancer: evasion from host-cell control in early events in carcinogenesis. J Natl Cancer Inst 92: 690-8, Tan S, et al. 2012. Anticancer drugs aimed at E6 and E7 activity in HPV-positive cervical cancer. Curr Cancer Drug Targets 12: 170-84).
CD4+ Th cells are known to play critical roles in the generation of CTL immune responses as well as memory T cell responses (Wiesel M, Oxenius A. 2012. From crucial to negligible: functional CD8(+) T-cell responses and their dependence on CD4(+) T-cell help. Eur J Immunol 42: 1080-8; Williams M A, et al. 2006. Developing and maintaining protective CD8+ memory T cells. Immunol Rev 211: 146-53). CD4+ T cell help prevents peptide-specific tolerance of CD8+ T cells (Shafer-Weaver K A, et al. 2009. Immunity to murine prostatic tumors: continuous provision of T-cell help prevents CD8 T-cell tolerance and activates tumor-infiltrating dendritic cells. Cancer Res 69: 6256-64). Further, tumor-specific CD4+ T cells may aid recruitment and cytolytic function of CD8+ T cells in the tumor microenvironment (Bos R, Sherman L A. 2010. CD4+ T-cell help in the tumor milieu is required for recruitment and cytolytic function of CD8+ T lymphocytes. Cancer Res 70: 8368-77). Moreover, CD4+ T cells, in absence of CD8+ T cells, may execute direct cytotoxic functions in a peptide-specific and HLA class II-restricted manner (van de Berg P J, et al. Cytotoxic human CD4(+) T cells. Curr Opin Immunol 20: 339-43; Brown D M. 2010. Cytolytic CD4 cells: Direct mediators in infectious disease and malignancy. Cell Immunol 262: 89-95). This might be relevant to HPV-induced lesions, as HLA class I surface expression can be reduced as a result of HPV immune evasion strategies (Grabowska A K, Riemer A B. 2012. The invisible enemy—how human papillomaviruses avoid recognition and clearance by the host immune system. Open Virol J 6: 249-56). In contrast, HLA class II molecules are expressed in high-grade cervical lesions and cervical carcinoma (Coleman N, Stanley M A. 1994. Analysis of HLA-DR expression on keratinocytes in cervical neoplasia. Int J Cancer 56: 314-9; Zhou J H, et al. 2006. Altered expression of cellular membrane molecules of HLA-DR, HLA-G and CD99 in cervical intraepithelial neoplasias and invasive squamous cell carcinoma. Life Sci 78: 2643-9). It has further been shown that the most effective induction of CTL immune responses requires T helper cells recognizing the same cognate antigen, rather than an unrelated Th stimulus (Bennett S R, et al. 1997. Induction of a CD8+ cytotoxic T lymphocyte response by cross-priming requires cognate CD4+ T cell help. J Exp Med 186: 65-70). Therefore, the inventors believe that for rational design of immunotherapeutic approaches against HPV-mediated lesions is beneficial to identify and provide CD4+ T helper cell epitopes derived from HPV target antigens. Most studies on identification of HPV-specific Th epitopes so far have been focusing on E6 and E7 as target antigens and overlapping peptide pools have been used rather than defined peptide epitopes (for review see Wang X, et al. A novel CD4 T-cell epitope described from one of the cervical cancer patients vaccinated with HPV 16 or 18 E7-pulsed dendritic cells. Cancer Immunol Immunother 58: 301-8; Welters M J, et al. 2006. Detection of human papillomavirus type 18 E6 and E7-specific CD4+ T-helper 1 immunity in relation to health versus disease. Int J Cancer 118: 950-6; Peng S, et al. 2007. HLA-DQB1*02-restricted HPV-16 E7 peptide-specific CD4+ T-cell immune responses correlate with regression of HPV-16-associated high-grade squamous intraepithelial lesions. Clin Cancer Res 13: 2479-87; van der Burg S H, et al. 2001. Natural T-helper immunity against human papillomavirus type 16 (HPV16) E7-derived peptide epitopes in patients with HPV16-positive cervical lesions: identification of 3 human leukocyte antigen class II-restricted epitopes. Int J Cancer 91: 612-8; Gallagher K M, Man S. 2007. Identification of HLA-DR1- and HLA-DR15-restricted human papillomavirus type 16 (HPV16) and HPV18 E6 epitopes recognized by CD4+ T cells from healthy young women. J Gen Virol 88: 1470-8). Although successful, these approaches of systematic T cell epitope mapping are costly and time-consuming, as they require synthesis and several rounds of screening of peptides spanning the full length of the target antigen.
U.S. Pat. No. 8,252,893 B2 describes CD8 T cell epitopes in the E6 and E7 protein of Human Papilloma-virus (HPV). U.S. Pat. No. 7,026,443 B1 discloses human papillomavirus (HPV) epitopes, pharmaceutical compositions and methods of use in the prevention and treatment of HPV infection. EP2167137A1 discloses HPV polyepitope constructs and the use thereof for the prevention and/or treatment of HPV infection.
The identification and characterization of HPV-associated antigens recognized by CD4-positive T cells (ligand: MHC class II molecule+peptide epitope) is important for the further development of HPV vaccines. It is therefore an object of the present invention, to provide novel amino acid sequences for HPV-derived peptides that are able to bind to MHC complexes of class II.
In a first aspect thereof, the invention provides a peptide comprising a sequence selected from the group of SEQ ID Nos. 26, 17, 28, 30, 1 to 16, 18 to 25, 27, 29, and 31 or a variant thereof which is 80% homologous, preferably 90%, and most preferred 95% homologous to any of SEQ ID Nos. 26, 17, 28, 30, 1 to 16, 18 to 25, 27, 29, and 31, wherein said peptide or variant thereof has the ability to bind to a molecule of the human major histocompatibility complex (MHC) class-II. In other variants, one or two amino acids at the N- and/or C-terminal end of a sequence selected from the group of SEQ ID Nos. 26, 17, 28, 30, 1 to 16, 18 to 25, 27, 29, and 31 can be replaced with another amino acid (preferably having the same or similar characteristics), wherein said variant maintains the ability to bind to a molecule of the human major histocompatibility complex (MHC) class-II, preferably the same as the underlying sequence selected from the group of SEQ ID Nos. 26, 17, 28, 30, 1 to 16, 18 to 25, 27, 29, and 31 (see also below).
In the present invention, the term “homologous” refers to the degree of identity between sequences of two amino acid sequences, i.e. peptide or polypeptide sequences. The aforementioned “homology” is determined by comparing two sequences aligned under optimal conditions over the sequences to be compared. The sequences to be compared herein may have an addition or deletion (for example, gap and the like) in the optimum alignment of the two sequences. Such a sequence homology can be calculated by creating an alignment using, for example, the ClustalW algorithm (Nucleic Acid Res., 22(22): 4673 4680 (1994)). Commonly available sequence analysis software, more specifically, Vector NTI, GENETYX or analysis tools provided by public databases, such as e.g. http://dragon.bio.purdue.edu/bioinfolinks/ may also be used.
Table A shows the peptides according to the invention, and their respective SEQ ID NOs.
SEQ ID NO:Peptide Sequence 1PRKLPQLCTELQTTI  2QQLLRREVYDFAFRD  3FRDLCIVYRDGNPYA  4LKFYSKISEYRHYCY  5GTTLEQQYNKPLCDL  6KQRFHNIRGRWTGRC  7MLDLQPETTDLYCYE  8STLRLCVQSTHVDIR  9TLRLCVQSTHVDIRT 10STHVDIRTLEDLLMG 11HVDIRTLEDLLMGTL 12IRTLEDLLMGTLGIV 13RDHIDYWKHMRLECA 14FKHINHQVVPTLAVS 15VPTLAVSKNKALQAI 16QLTLETIYNSQYSNE 17LEVYLTAPTGCIKKH 18GLYYVHEGIRTYFVQ 19PEIIRQHLANHPAAT 20ILTAFNSSHKGRINC 21IVHLKGDANTLKCLR 22CLRYRFKKHCTLYTA 23DQFLSQVKIPKTITV 24MTNLDTASTTLLACF 25RPLLLSVSTYTSLIL 26LLSVSTYTSLILLVL 27LVLVLWITAASAFRC 28ASAFRCFIVYIVFVY 29FIVYIVFVYIPLFLI 30VYIPLFLIHTHARFL 31IPLFLIHTHARFLIT
Preferred are the following sequences (table A1):
SEQ ID NO:Peptide Sequence 3FRDLCIVYRDGNPYA  4LKFYSKISEYRHYCY  7MLDLQPETTDLYCYE  9TLRLCVQSTHVDIRT 12IRTLEDLLMGTLGIV 17LEVYLTAPTGCIKKH 18GLYYVHEGIRTYFVQ 26LLSVSTYTSLILLVL 28ASAFRCFIVYIVFVY 30VYIPLFLIHTHARFL
Most preferred are the following sequences (table A2):
SEQ ID NO:Peptide Sequence 4LKFYSKISEYRHYCY  7MLDLQPETTDLYCYE  9TLRLCVQSTHVDIRT 18GLYYVHEGIRTYFVQ 26LLSVSTYTSLILLVL
Thus, the invention also relates to a combination of peptides according to the invention, comprising at least two, preferably three, four or five peptides consisting of an amino acid sequence selected from the group of SEQ ID Nos. 26, 9, 7, 4, and 18, in particular in the form of a vaccine such as, for example, a cancer vaccine.
In the present study, with the help of immuno-bioinformatic approaches, the inventors identified several candidate HPV16 E2-, E5-, E6-, and E7-derived CD4+ T cell epitopes promiscuously presented by multiple HLA-DR alleles and evaluated their immunogenicity in healthy individuals. The inventors here present an approach to identify promiscuous HPV16-derived CD4+ T helper epitopes, which are able to induce T cell immunity in a large proportion of the population. To this end, the inventors combined HLA class II epitope prediction servers with ex vivo immunological evaluation to identify HPV16 E2-, E5-, E6-, and E7-derived CD4+ T cell epitopes. Candidate selected HPV16-derived epitopes were found to be restricted by up to nine out of eleven tested HLA-DR molecules. Furthermore, they were found to induce frequent and robust HPV16 peptide-specific T cell responses in the healthy donors, as monitored by IFN-γ ELISPOT and cytokine secretion assays. The observed HPV16 peptide-specific immunity was of the Th1 phenotype, and not associated with CD4+ regulatory T cells. Therefore, the inventors conclude that the identified T helper epitopes are valuable candidates for the development of a comprehensive therapeutic HPV vaccine.
By a “variant” of the given amino acid sequence the inventors mean that the side chains of, for example, one or two of the amino acid residues are altered (for example by replacing them with the side chain of another naturally occurring amino acid residue or some other side chain) so that the peptide is still able to bind to an HLA molecule in substantially the same way as a peptide consisting of the given amino acid sequence. For example, a peptide may be modified so that it at least maintains, if not improves, the ability to interact with and bind a suitable MHC molecule, such as HLA-DR, and so that it at least maintains, if not improves, the ability to generate activated CTL that can recognize and kill cells that express a polypeptide containing an amino acid sequence as defined in the aspects of the invention.
Those amino acid residues that are not essential to interact with the T-cell receptor can be modified by replacement with another amino acid whose incorporation does not substantially affect T-cell reactivity and does not eliminate binding to the relevant MHC. Thus, apart from the proviso given, the peptide of the invention may be any peptide (by which term the inventors include oligopeptide or polypeptide) which includes the amino acid sequences or a portion or variant thereof as given.
It is furthermore known for MHC-class II presented peptides that these peptides are composed of a “core sequence” having a certain HLA-specific amino acid motif and, optionally, N- and/or C-terminal extensions which do not interfere with the function of the core sequence (i.e. are deemed irrelevant for the interaction of the peptide and all or a subset of T-cell clones recognizing the natural counterpart). The N- and/or C-terminal extensions can, for example, be between 1 to 10 amino acids in length, respectively. These peptides can be used either directly to load MHC class II molecules or the sequence can be cloned into the vectors according to the description herein below. As these peptides constitute the final product of the processing of larger peptides within the cell, longer peptides can be used as well. The peptides of the invention may be of any size, but typically they may be less than 5.000 in molecular weight. In terms of the number of amino acid residues, the peptides of the invention may have fewer than 50 residues. Accordingly the present invention also provides peptides and variants thereof wherein the peptide or variant has an overall length of between 15 and 50, preferably between 15 and 30, and most preferred between 15 and 20 amino acids, namely 15, 16, 17, 18, 19, or 20 amino acids
Binding of a peptide or a variant to a MHC complex may be tested by methods known in the art, for example those described in example 4 of the present invention or those described in the literature for different MHC class II alleles (e.g. Vogt A B, et al. Ligand motifs of HLA-DRB5*0101 and DRB1*1501 molecules delineated from self-peptides; J Immunol. 1994; 153(4):1665-1673; Malcherek G, et al. Analysis of allele-specific contact sites of natural HLA-DR17 ligands; J Immunol. 1994; 153(3):1141-1149; Manici S, et al. Melanoma cells present a MAGE-3 epitope to CD4(+) cytotoxic T cells in association with histocompatibility leukocyte antigen DR11; J Exp Med. 1999; 189(5): 871-876; Hammer J, et al. Peptide binding specificity of HLA-DR4 molecules: correlation with rheumatoid arthritis association; J. Exp Med. 1995 181(5):1847-1855; Tompkins S M, Rota P A, Moore J C, Jensen P E; A europium fluoroimmunoassay for measuring binding of antigen to class II MHC glycoproteins; J Immunol Methods. 1993; 163(2): 209-216; Boyton R J, et al. Glutamic acid decarboxylase T lymphocyte responses associated with susceptibility or resistance to type I diabetes: analysis in disease discordant human twins, non-obese diabetic mice and HLA-DQ transgenic mice; Int Immunol. 1998 (12):1765-1776).
The peptides of the present invention or variants thereof are expected to stimulate CD4+ T cells.
In a particularly preferred embodiment of the invention the peptide consists or consists essentially of an amino acid sequence according to SEQ ID Nos. 26, 17, 28, 30, 1 to 16, 18 to 25, 27, 29, and 31. “Consisting essentially of” shall mean that a peptide according to the present invention, in addition to the sequence according to any of SEQ ID Nos. 26, 17, 28, 30, 1 to 16, 18 to 25, 27, 29, and 31 or a variant thereof, contains additional N- and/or C-terminally located stretches of amino acids that are not necessarily forming part of the peptide that functions as an epitope for MHC molecules epitope.
In a particularly preferred embodiment of the invention, the peptide of the invention has an IC50: 60≤1000 nM, and preferably an IC50≤60 nM for an HLA-DR allele.
In addition the peptide or variant may be modified further to improve stability and/or binding to MHC molecules to elicit a stronger immune response. Methods for such an optimization of a peptide sequence are well known in the art and include, for example, the introduction of reverse peptide bonds or non-peptide bonds.
A non-peptide bond is, for example, —CH2—NH, —CH2CH2—, —CH═CH—, —COCH2—, —CH(OH)CH2—, and —CH2SO—. U.S. Pat. No. 4,897,445 provides a method for the solid phase synthesis of non-peptide bonds (—CH2—NH) in polypeptide chains that involves polypeptides synthesized by standard procedures and the non-peptide bond synthesized by reacting an amino aldehyde and an amino acid in the presence of NaCNBH3.
Similarly, a peptide or variant of the invention may be modified chemically by reacting specific amino acids either before or after synthesis of the peptide. Examples for such modifications are well known in the art and are summarized e.g. in R. Lundblad, Chemical Reagents for Protein Modification, 3rd ed. CRC Press, 2005, which is incorporated herein by reference. Chemical modification of amino acids includes but is not limited to, modification by acylation, amidination, pyridoxylation of lysine, reductive alkylation, trinitrobenzylation of amino groups with 2,4,6-trinitrobenzene sulphonic acid (TNBS), amide modification of carboxyl groups and sulphydryl modification by performic acid oxidation of cysteine to cysteic acid, formation of mercurial derivatives, formation of mixed disulphides with other thiol compounds, reaction with maleimide, carboxymethylation with iodoacetic acid or iodoacetamide and carbamoylation with cyanate at alkaline pH, although without limitation thereto. In this regard, the skilled person is referred to Chapter 15 of Current Protocols In Protein Science, Eds. Coligan et al. (John Wiley & Sons NY 1995-2000) for more extensive methodology relating to chemical modification of proteins.
Generally, peptides and variants (at least those containing peptide linkages between amino acid residues) may be synthesized by the Fmoc-polyamide mode of solid-phase peptide synthesis as disclosed by Lu et al J. Org. Chem. 1981, 46, 3433, and references therein, as well as through other methods known in the art. Purification may be effected by any one, or a combination of, techniques such as re-crystallization, size exclusion chromatography, ion-exchange chromatography, hydrophobic interaction chromatography and (usually) reverse-phase high performance liquid chromatography using e.g. acetonitril/water gradient separation.
A further aspect of the invention provides a nucleic acid (e.g. polynucleotide) encoding a peptide or variant of the invention. The polynucleotide may be e.g. DNA, cDNA, PNA, CNA, RNA, mRNA, and siRNA or combinations thereof, either single- and/or double-stranded, or native or stabilised forms of polynucleotides, such as e.g. polynucleotides with a phosphorothiate backbone, and it may or may not contain introns so long as it codes for the peptide. Of course, only peptides containing naturally occurring amino acid residues joined by naturally occurring peptide bonds are encodable by a polynucleotide. A still further aspect of the invention provides an expression vector capable of expressing a polypeptide according to the invention. A variety of methods have been developed to operably link polynucleotides, especially DNA, to vectors for example via complementary cohesive termini. For instance, complementary homopolymer tracts can be added to the DNA segment to be inserted to the vector DNA. The vector and DNA segment are then joined by hydrogen bonding between the complementary homopolymeric tails to form recombinant DNA molecules.
If viral vectors are used, herpes-, pox- or adenovirus vectors are preferred.
The DNA (or in the case of retroviral vectors, RNA) may then be expressed in a suitable host to produce a polypeptide comprising the peptide or variant of the invention. Thus, the DNA encoding the peptide or variant of the invention may be used in accordance with known techniques, appropriately modified in view of the teachings contained herein, to construct an expression vector, which is then used to transform an appropriate host cell for the expression and production of the polypeptide of the invention.
The DNA (or in the case of retroviral vectors, RNA) encoding the polypeptide constituting the compound of the invention may be joined to a wide variety of other DNA sequences for introduction into an appropriate host. The companion DNA will depend upon the nature of the host, the manner of the introduction of the DNA into the host, and whether episomal maintenance or integration is desired.
In another embodiment the peptide according to the invention, the nucleic acid according to the invention or the expression vector according to the invention are used in medicine. For example, the peptide or its variant may be prepared for intravenous (i.v.) injection, subcutaneous (s.c.) injection, intradermal (i.d.) injection, intraperitoneal (i.p.) injection, intramuscular (i.m.) injection. Preferred routes of peptide injection are s.c., i.d., i.p., i.m., and i.v. Preferred routes of DNA injection are i.d., i.m., s.c., i.p. and i.v. Doses of e.g. between 50 μg and 1.5 mg, preferably 125 μg to 500 μg, of peptide or DNA may be given and will depend from the respective peptide or DNA.
Preferably, the peptides of the invention are produced synthetically, or at least in part synthetically, using well-established peptide synthesis technology.
The present invention also relates to a host cell transformed with a polynucleotide vector construct of the present invention. The host cell thus comprises the nucleic acid according to the invention or the expression vector according to the invention. The host cell can be either prokaryotic or eukaryotic. Bacterial cells may be preferred prokaryotic host cells in some circumstances and typically are a strain of E. coli such as, for example, the E. coli strains DH5 available from Bethesda Research Laboratories Inc., Bethesda, Md., USA, and RR1 available from the American Type Culture Collection (ATCC) of Rockville, Md., USA (No ATCC 31343). Preferred eukaryotic host cells include yeast, insect and mammalian cells, preferably vertebrate cells such as those from a mouse, rat, monkey or human. Yeast host cells include YPH499, YPH500 and YPH501 which are generally available from Stratagene Cloning Systems, La Jolla, Calif. 92037, USA. Preferred mammalian host cells include Chinese hamster ovary (CHO) cells available from the ATCC as CCL61, NIH Swiss mouse embryo cells NIH/3T3 available from the ATCC as CRL 1658, monkey kidney-derived COS-1 cells available from the ATCC as CRL 1650 and 293 cells which are human embryonic kidney cells. Preferred insect cells are Sf9 cells which can be transfected with baculovirus expression vectors. Transformation of appropriate cell hosts with a DNA construct of the present invention is accomplished by well-known methods that typically depend on the type of vector used.
A further aspect of the invention provides a method of producing a peptide or its variant. The method comprises culturing the host cell of the invention, and isolating the peptide from the host cell or the culture medium.
Another aspect of the present invention relates to a vaccine comprising the host cells as described herein, which in a preferred embodiment is a life vaccine. In such an embodiment, the host cell can be an antigen presenting cell, in particular a dendritic cell. APCs loaded with a recombinant fusion protein containing prostatic acid phosphatase (PAP) are approved for the treatment of prostate cancer (Sipuleucel-T) (see, e.g., Cheever M A, Higano C S. PROVENGE (Sipuleucel-T) in prostate cancer: the first FDA-approved therapeutic cancer vaccine. Clin Cancer Res. 2011 Jun. 1; 17(11):3520-6; Epub 2011 Apr. 6).
Another aspect of the present invention is an in vitro method for inducing activated T helper (TH) cells, comprising contacting in vitro TH cells with antigen loaded human class II MHC molecules expressed on the surface of a suitable antigen-presenting cell for a period of time sufficient to activate said TH cells in an antigen specific manner, wherein said antigen is a peptide according to the invention. Preferably, a sufficient amount of the antigen is used with an antigen-presenting cell.
The MHC class II molecules may be expressed on the surface of any suitable cell. Thus, the antigen-presenting cell (or stimulator cell) typically has MHC class II molecules on its surface. The MHC class II molecule may readily be loaded with the selected antigen in vitro. In case of MHC II epitopes as antigens, the T cells are CD4-positive T-helper cells.
A number of methods for generating activated T cells in vitro are described in the respective literature.
The activated TH cells that are directed against the peptides of the invention are useful in therapy. Thus, a further aspect of the invention provides activated TH cells, produced and obtainable by the method according to the invention, which selectively recognizes a cell which expresses an HPV polypeptide comprising an amino acid sequence according to SEQ ID Nos. 26, 17, 28, 30, 1 to 16, 18 to 25, 27, 29, or 31.
The TH cells of the invention may be used as active ingredients in a therapeutic composition. Thus the invention also provides a method of killing target cells in a patient where the target cells express a polypeptide comprising an amino acid sequence of the invention. The method comprises administering to the patient an effective number of TH cells as defined above.
TH cells may be obtained by methods known in the art, e.g. those described above.
Any molecule of the invention, i.e. the peptide, nucleic acid, expression vector, cell, activated TH cells, T-cell receptor or the nucleic acid encoding it is useful for the treatment of HPV-related disorders, characterized by cells escaping an immune response. Therefore any molecule of the present invention may be used as medicament or in the manufacture of a medicament. The molecule may be used by itself or combined with other molecule(s) of the invention or (a) known molecule(s).
An important aspect of the present invention is therefore a pharmaceutical preparation, comprising at least one of the peptide according to the invention, the nucleic acid according to the invention, the expression vector according to the invention, the host cell according to the invention, the activated TH lymphocyte according to the invention, and a pharmaceutically acceptable excipient, wherein preferably said pharmaceutical preparation is a vaccine.
Preferably the medicament is a vaccine. It may be administered directly into the patient, into the affected organ or systemically, or applied ex vivo to cells derived from the patient or a human cell line which are subsequently administered to the patient, or used in vitro to select a subpopulation from immune cells derived from the patient, which are then re-administered to the patient. If the nucleic acid is administered to cells in vitro, it may be useful for the cells to be transfected so as to co-express immune-stimulating cytokines, such as interleukin-2 The peptide may be substantially pure, or combined with an immune-stimulating adjuvant (see below) or used in combination with immune-stimulatory cytokines, or be administered with a suitable delivery system, for example nanoparticles or liposomes. The peptide may also be conjugated to a suitable carrier such as keyhole limpet haemocyanin (KLH) or mannan (see WO 95/18145 and Longenecker et al. (1993) Ann. NY Acad. Sci. 690, 276-291).
Thus, in another aspect of the invention, the peptide according to the invention is part of a fusion protein or fusion molecule, e.g. with a TLR ligand.
In one aspect of the invention, the vaccine comprises at least one peptide, preferably two to 31, more preferably two to 25, even more preferably two to 15 and most preferably two, three, four, five, six, seven, eight, nine, ten, eleven, twelve or thirteen peptides of the invention or additional peptides. The peptide(s) may be derived from one or more specific HPV antigen, and may bind to MHC class I and/or class II molecules.
Particularly preferred vaccines include peptides according to the present invention that show an IC50≤60 nM for an HLA-DR allele.
More preferred is an HPV vaccine comprising at least one, preferably all, of the following peptides (table A3):
SEQ ID NO:Peptide Sequence 3FRDLCIVYRDGNPYA  4LKFYSKISEYRHYCY  7MLDLQPETTDLYCYE  9TLRLCVQSTHVDIRT 12IRTLEDLLMGTLGIV 17LEVYLTAPTGCIKKH 18GLYYVHEGIRTYFVQ 26LLSVSTYTSLILLVL 28ASAFRCFIVYIVFVY 30VYIPLFLIHTHARFL
Most preferred is an HPV vaccine comprising at least one, preferably all, of the following peptides (table A4):
SEQ ID NO:Peptide Sequence 4LKFYSKISEYRHYCY  7MLDLQPETTDLYCYE  9TLRLCVQSTHVDIRT 18GLYYVHEGIRTYFVQ 26LLSVSTYTSLILLVL
The medicament of the invention may also include one or more adjuvants. Adjuvants are substances that non-specifically enhance or potentiate the immune response (e.g. immune responses mediated by CTLs and helper-T (TH) cells to an antigen, and would thus be considered useful in the medicament of the present invention.
Suitable adjuvants include, but are not limited to aluminum salts, TLR agonists, or GM-CSF or other commercial adjuvants.
When the peptides of the invention are used in a vaccine or medicament of the invention, they are present as a salt, such as for example, but not limited to an acetate salt or a chloride salt.
Another aspect of the invention then relates to the peptide according to the invention, the nucleic acid according to the invention, the expression vector according to the invention, the host cell according to the invention, the activated TH cell according to the invention, or the pharmaceutical preparation according to the invention for use in the treatment of HPV infection, and HPV-related pre-malignancies and/or malignancies.
Yet another aspect of the invention relates to a method of killing target cells in a patient which target cells express an HPV polypeptide comprising an amino acid sequence as given for the peptides herein, the method comprising administering to the patient an effective number of TH cell according to the invention.
In yet another aspect thereof, the present invention relates to a kit comprising (a) a container that contains a pharmaceutical composition as described above, in solution or in lyophilized form; (b) optionally, a second container containing a diluent or reconstituting solution for the lyophilized formulation; and (c) optionally, instructions for (i) use of the solution or (ii) reconstitution and/or use of the lyophilized formulation. Said kit may further comprise one or more of (iii) a buffer, (iv) a diluent, (v) a filter, (vi) a needle, or (v) a syringe. The container is preferably a bottle, a vial, a syringe or test tube; and it may be a multi-use container. The pharmaceutical composition is preferably lyophilized.
Kits of the present invention preferably comprise a lyophilized formulation of the present invention in a suitable container and instructions for its reconstitution and/or use. Suitable containers include, for example, bottles, vials (e.g. dual chamber vials), syringes (such as dual chamber syringes) and test tubes. The container may be formed from a variety of materials such as glass or plastic. Preferably the kit and/or container contains instructions on or associated with the container that indicates directions for reconstitution and/or use. For example, the label may indicate that the lyophilized formulation is to reconstituted to peptide concentrations as described above.
Numerous reports demonstrate the importance of both CD8+ and CD4+ T cells in the clearance of HPV infection as well as in the protection against developing HPV-associated malignancies (10-13). However, the development of successful anti-HPV immunotherapy has proved to be a challenging task. Recently, there has been considerable interest to identify HPV E6 and E7-derived CD4+ T helper cell epitopes using overlapping peptide pools and to include them in therapeutic peptide-based therapeutic vaccine design (34-38). The inventors' approach in the current work was to use computational HLA class II prediction algorithms to define a 15-mer HPV16-derived CD4+ T cell epitopes that bind promiscuously to the binding groove of multiple HLA-DR molecules. The inventors performed predictions for eleven alleles, namely DRB1*0101, DRB1*0301, DRB1*0401, DRB1*0701, DRB1*0901, DRB1*1101, DRB1*1302, DRB1*1501, DRB3*0101, DRB4*0101 and DRB5*0101. Candidate promiscuous epitopes were evaluated in vitro for their potential to elicit immune responses in healthy subjects. As most sexually active individuals are infected transiently with at least one high-risk HPV type during their life (Woodman C B, Collins S I, Young L S. 2007. The natural history of cervical HPV infection: unresolved issues. Nat Rev Cancer 7: 11-22, Evander M, et al. 1995. Human papillomavirus infection is transient in young women: a population-based cohort study. J Infect Dis 171: 1026-30), previous HPV exposure of the donors is likely.
The use of prediction servers has several advantages over using overlapping peptide pools. Testing overlapping epitopes spanning the full length of a protein is a time-consuming approach even when testing only one HLA type, but even more so when several HLA molecules have to be interrogated for the identification of promiscuously binding epitopes. Thus, in the present study, the inventors took advantage of two HLA class II epitope prediction servers, SYFPEITHI and NetMHCII. This allowed them to screen in silico for candidate peptides binding to several HLA class II molecules. Only peptides predicted to bind to five or more HLA-DR molecules were further analyzed, thus focusing immune assays to the most promising candidates. As the accuracy of prediction servers is not absolute, it is recommendable to use more than one, to ensure that no potential binder is missed. Also in this study, it can be seen that the results from the two prediction servers were not completely consistent. The combined use of both let to the inclusion of peptides that would not have been found by applying only one prediction algorithm.
Up to now, most studies focused on the identification of epitopes derived from the HPV oncoproteins E6 and E7, in the context of peptide-based immunotherapy against advanced lesions in the patients (Wang X, et al. 2009. A novel CD4 T-cell epitope described from one of the cervical cancer patients vaccinated with HPV 16 or 18 E7-pulsed dendritic cells. Cancer Immunol Immunother 58: 301-8; Welters M J, et al. 2006. Detection of human papillomavirus type 18 E6 and E7-specific CD4+ T-helper 1 immunity in relation to health versus disease. Int J Cancer 118: 950-6; Peng S, et al. 2007. HLA-DQB1*02-restricted HPV-16 E7 peptide-specific CD4+ T-cell immune responses correlate with regression of HPV-16-associated high-grade squamous intraepithelial lesions. Clin Cancer Res 13: 2479-87; van der Burg S H, et al. 2001. Natural T-helper immunity against human papillomavirus type 16 (HPV16) E7-derived peptide epitopes in patients with HPV16-positive cervical lesions: identification of 3 human leukocyte antigen class II-restricted epitopes. Int J Cancer 91: 612-8; Gallagher K M, Man S. 2007. Identification of HLA-DR1- and HLA-DR15-restricted human papillomavirus type 16 (HPV16) and HPV18 E6 epitopes recognized by CD4+ T cells from healthy young women. J Gen Virol 88: 1470-8). To the best of the inventors' knowledge, there is only one study reporting CD4+ T cell epitopes for HPV16 E2 (de Jong A, et al. 2002. Frequent detection of human papillomavirus 16 E2-specific T-helper immunity in healthy subjects. Cancer Res 62: 472-9), and no studies on E5-derived T helper epitopes. None of these studies deal with the identification of promiscuous CD4+ T cell epitopes. As the inclusion of such epitopes in any peptide-based therapeutic HPV vaccine is expected to increase immunogenicity and efficacy, the inventors here aimed to identify promiscuous T helper epitopes derived from HPV16 E2, E5, E6 and E7.
Overall, the inventors found that 13 out of the 31 predicted promiscuously binding HPV16-derived HLA class II peptides (Table 1) were recognized by at least 30% of healthy donors in short-term ex vivo ELISPOT assays (Tables 2 and 3). The inventors identified seven novel HPV16 15-mer CD4+ T cell epitopes, namely E2/76-90, E5/33-48, E5/45-60, E5/54-69, E5/60-74, E5/67-81 and E7/12-26. The epitopes E6/54-68, E6/74-88, E7/64-78, E7/71-85, E2/99-113 and E2/156-170 are part of previously reported long peptides (Welters M J, et al. 2003. Frequent display of human papillomavirus type 16 E6-specific memory t-Helper cells in the healthy population as witness of previous viral encounter. Cancer Res 63: 636-41, Wang X, et al. A novel CD4 T-cell epitope described from one of the cervical cancer patients vaccinated with HPV 16 or 18 E7-pulsed dendritic cells. Cancer Immunol Immunother 58: 301-8, Peng S, et al. 2007. HLA-DQB1*02-restricted HPV-16 E7 peptide-specific CD4+ T-cell immune responses correlate with regression of HPV-16-associated high-grade squamous intraepithelial lesions. Clin Cancer Res 13: 2479-87, de Jong A, et al. 2002. Frequent detection of human papillomavirus 16 E2-specific T-helper immunity in healthy subjects. Cancer Res 62: 472-9), supporting the inventors' approach of epitope detection. Each peptide was predicted to bind to five to nine different HLA class II molecules out of the eleven tested in this study, and found to elicit immune responses in individuals carrying the respective HLA class II alleles (Table 4). Only three subjects showed reactivity towards a peptide that was not predicted to bind to any of his/her HLA-DR molecules. This reactivity could be due to HLA-DP or -DQ peptide presentation, or HLA class I restricted epitopes contained in the respective 15-mers (see below). Another interesting finding was the high proportion of HPV16 E7-specific CD4+ T cell responses in the cohort, although it has been reported that E7-reactivity is rarely observed in healthy individuals (Welters M J, et al. 2003. Frequent display of human papillomavirus type 16 E6-specific memory t-Helper cells in the healthy population as witness of previous viral encounter. Cancer Res 63: 636-41 van der Burg S H, et al. 2001. Natural T-helper immunity against human papillomavirus type 16 (HPV16) E7-derived peptide epitopes in patients with HPV16-positive cervical lesions: identification of 3 human leukocyte antigen class II-restricted epitopes. Int J Cancer 91: 612-8; Gallagher K M, Man S. 2007. Identification of HLA-DR1- and HLA-DR15-restricted human papillomavirus type 16 (HPV16) and HPV18 E6 epitopes recognized by CD4+ T cells from healthy young women. J Gen Virol 88: 1470-8).
Based on ELISPOT reactivities (FIG. 1), five epitopes were selected for detailed analysis. HLA class II restriction of the HPV16 peptide-specific T cell responses was confirmed by abrogation of IFN-γ production in the presence of an HLA-DR blocking antibody (FIG. 2). Possible HLA-DQ and HLA-DP restriction of the selected peptides was not assessed in the inventors' study. Regarding the phenotype of HPV16 peptide-specific T cell immunity, the inventors' results from CD4+ and CD8+ T cell depletion (FIG. 3) and intracellular cytokine staining experiments provide strong evidence that the responding T cells are indeed CD4+ T cells. The profile of cytokine secretion of HPV16 peptide-specific CD4+ T cells was found to be of the Th1 type (IFN-γ, TNF-α, GM-CSF) (FIG. 4A), which is associated with control and clearance of HPV infections (Scott M, Stites D P, Moscicki A B. 1999. Th1 cytokine patterns in cervical human papillomavirus infection. Clin Diagn Lab Immunol 6: 751-5; Bais A G, et al. 2007. Cytokine release in HR-HPV(+) women without and with cervical dysplasia (CIN II and III) or carcinoma, compared with HR-HPV(−) controls. Mediators Inflamm 2007: 24147). Moreover, the inventors observed only low percentages of HPV16 peptide-specific CD4+ regulatory T cells (FIG. 4B and FIG. 5), which is also associated with a favorable disease outcome (van der Burg S H, et al. 2007. Association of cervical cancer with the presence of CD4+ regulatory T cells specific for human papillomavirus antigens. Proc Natl Acad Sci USA 104: 12087-92; Kim K H, et al. 2012. CD4+ T-cell response against human papillomavirus type 16 E6 protein is associated with a favorable clinical trend. Cancer Immunol Immunother 61: 63-70; Visser J, et al. 2007. Frequencies and role of regulatory T cells in patients with (pre)malignant cervical neoplasia. Clin Exp Immunol 150: 199-209). As the inventors tested healthy donors who are likely to have cleared HPV infection in their past, these results are promising that the inventors' strategy indeed identifies peptides involved in viral clearance.
CD4+ T cells have recently been reported to be capable of direct cytotoxic functions (van de Berg P J, et al. 2008. Cytotoxic human CD4(+) T cells. Curr Opin Immunol 20: 339-43; Brown D M. 2010. Cytolytic CD4 cells: Direct mediators in infectious disease and malignancy. Cell Immunol 262: 89-95), therefore perforin/granzyme B release as well as CD107a expression analyses were performed. However, no HPV16-derived peptide-specific CD4+ T cell-mediated cytotoxic activity was observed in this cohort of healthy individuals (data not shown). This observation might reflect the fact that cytotoxic activity of T helper cells arises only during acute or persistent infections or in the presence of malignancies (Brown D M. 2010. Cytolytic CD4 cells: Direct mediators in infectious disease and malignancy. Cell Immunol 262: 89-95).
Importantly, it is possible that defined CD4+ T cell epitopes harbor HLA class I-restricted immunogenic regions. HLA class II-restricted epitopes that contain HLA class I epitopes in their sequence could be highly useful for effective peptide-based immunotherapies, as both CD4+ and CD8+ T cell responses may be simultaneously induced.
In summary, the inventors have defined 13 promiscuous 15-mer HPV16-derived CD4+ T cell epitopes, seven of which have not been described before. The inventors show that selected epitopes indeed are promiscuous and immunogenic, inducing Th1 cells in healthy individuals with a diverse genetic background. The inventors conclude that the identified T helper epitopes are candidates for the development of a comprehensive epitope-specific therapeutic HPV vaccine against established premalignant as well as advanced lesions.
SEQ ID NO: 1 to 31 show peptide sequences of HPV-related antigens and epitopes according to the invention.